Forage harvesters are used for harvesting whole plants or their parts that are taken up, during operation, from a field by means of a harvesting attachment, pressed together by pre-press rollers, and fed to a blade drum whose chopping blades cut up the plants in conjunction with a counter blade. Then the cut-up plants or plant parts are optionally fed to a secondary cutting device and conveyed by a secondary acceleration device into a discharge bend that loads it over onto a transport vehicle. The cut-up plants are typically used as fodder and/or biogas production.
In the case of a known embodiment as disclosed in German Patent Document DE 199 18 553 A1, the chopping drum comprises a drum body on which blade holders are welded, with the chopping blades being screwed, in turn, onto these holders. The drum body is connected by end plates or spokes to a central shaft that is mounted so that it can rotate and can be driven. In this way, a relatively high expense for the production of the weld connections is required between the drum body and the blade holders for them to be produced with sufficient accuracy, in order to allow low out-of-balance spinning of the chopping drum and to have to remove as little material as possible from the chopping blades when grinding the chopping blades with a grinding device. In addition, the weld connections form structural weak points that can be repaired only with difficulty or not at all in the case of wear or damage.
Furthermore, European Patent Document EP 0 789 994 A1 describes another chopping drum in which a central shaft is connected to six supporting rings extending in the radial direction. The supporting rings are equipped on their periphery with threads in which screws are inserted that extend through corresponding boreholes into the blade holders and into plates forming the drum body and fix the plates and the blade holders attached to the plates onto the supporting rings on the outside. The chopping blades are mounted on the blade holders, in turn, by other screws. Here, the cutting forces are transmitted via the blade holders to the supporting rings, so that these are to be dimensioned to be sufficiently stable.
German Patent Document DE 88 13 953 U1 describes a chopping drum in which a central shaft is connected to three supporting rings extending in the radial direction. In one embodiment, the blade holders are welded with the supporting rings, and in another embodiment, panels are welded onto the supporting rings and the blade holders are screwed in with the panels. The chopping blades are screwed in, in turn, with the blade holders. German Patent Document DE 195 22 056 A1 shows a similar arrangement, wherein, however, the blade holders simultaneously form a segmented, outer lateral surface of the chopping drum. In the case of this prior art, it is considered disadvantageous that the forces are transmitted from the blade holders to the shaft only via the supporting rings, which is why the supporting rings are to be dimensioned with sufficient stability.